Colloidal nanocrystals (NCs) have recently gained attention for their applications in light emitting diodes, lasers, quantum dots, and solar cells. The ability to produce high quality colloidal NCs with high-throughput is a key step in the development of low-cost processing. The ability to control the uniformity of the size, shape, composition and crystal structure of the NCs is also of technological interest.
NCs are generally synthesized by thermal decomposition of the precursors in a mixture of solvents and coordinating ligands. The most common procedure for synthesizing high-quality NCs has utilized a “hot injection” method to achieve burst nucleation. The conductive heating methods (such as isomantles, oil baths, or hot plates) are performed using small volume flasks, leading to low production rates. Furthermore, vessel temperature and mass transfer characteristics are not well defined and significant variation is commonly observed, especially if the vessel size is enlarged. These problems make the commercial scaling up of NCs problematic. Producing colloidal NCs via a continuous method provides an opportunity to reduce the required production time and lower the cost per mass of synthesized colloidal NCs.
The use of microwaves in the synthesis of colloidal NCs eliminates thermal gradients by uniformly heating the solution volume, and can be used to direct energy input to more microwave active species leading to highly controllable reaction conditions. A continuous flow microwave reactor system may be used to prepare large quantities of NCs. However, continuous systems known in the art lead to sparking inside the microwave flow path due to deposition and early precipitation of the NCs in the microwave zone. These, and other issues, are solved by the systems and methods of the present invention.